A gas turbine engine generally includes a compressor section, a combustor section, a turbine section and an exhaust section. In operation, the compressor section inducts and compresses ambient air. The compressed air from the compressor section is directed to one or more combustors in the combustor section where it is mixed with the fuel and combusted to form a hot working gas. The hot working gas is routed to the turbine section where it is expanded through alternating rows of stationary airfoils and rotating airfoils and used to generate power that can drive a rotor. The expanded gas exiting the turbine section is exhausted from the engine via the exhaust section.
The exhaust section may be configured as a diffuser defined as annular divergent duct formed between inner and outer walls. The exhaust diffuser operates to reduce the speed of the exhaust flow and thus increase the pressure difference of the exhaust gas expanding across the last stage of the turbine. In addition, support struts may extend through the inner and outer walls to support a bearing housing radially inwardly from a casing surrounding the diffuser. Typically, the support struts are surrounded by covers or aerodynamic fairings to direct gas flow around the support struts and to protect the support struts from the hot working gases.
In current power plant operations, the power output from a gas turbine engine may be reduced from a base load operating condition, such as may be provided during a high power grid energy demand, to a part load operating condition, such as may occur during a reduced power grid energy demand during which power from a generator driven by the turbine engine may not be required. During part load operation, the turbine engine is typically operating at an efficiency that is below an optimum design efficiency provided during the base load operation.